attr

type Getter interface {
	GetInt(string) int
	GetString(string) string
	GetStrings(string) []string
}

type Interface interface {
	// Name returns the name of the attribute.
	Name() string

	// IsEmpty returns true iff `x` is a representation of the empty value of this attribute.
	IsEmpty(x interface{}) bool

	// Value returns the value of this attribute in `g`.
	Value(g Getter) interface{}

	// Intersect returns the intersection of `x` and `y`, assumed to be the type of the
	// attribute.
	Intersect(x, y interface{}) interface{}
}